Enlargement and area


Learning Objective:

  • we are learning to predict the effects of enlargement on the area of 2D shapes

Investing:

  • This is useful because when you use scale drawings and maps you are using a scale factor and enlargement and you may need to find areas from these diagrams.
  • A functional (real-life) application is finding the area of carpet if you know the area of a plan of a room at a given scale factor
  • This skill leads to converting units of area
  • This could help you if you want to work in architecture, interior design, farming, industrial design

Preparing:

  • Can you already enlarge a shape using a scale factor and centre of enlargement?
  • Before you start you need to know how to find the area of simple 2D shapes
  • You will have a deeper understanding if you also know a bit about ratios

Discovering:

  • Can you figure it out yourself from these examples?

  • Compare the areas of the small rectangle with the larger rectangle
  • Consider making a table of values
  • What is the area factor for a length factor 2?
  • For length factor 3?
  • And 4?

  • What's the pattern to this?

  • What will the area scale factor be for a length factor of 9?
  • What about 10?

Discussing:

  • What would this one be? Tell your learning partner. Convince them you're right.
  • Explain how you know.
  • How would you explain this to someone who was new to it?

Explaining:

  • Why does this work?

Developing and extending:

  • What will happen to the volume of 3D shapes that are enlarged?

last edited: Mar 17, 2014 10:09 am